In a motor-vehicle fuel system with high-pressure fuel injection, air entrained in the fuel can have various undesirable effects. Such effects include engine hesitation and stalling, difficulty starting, and damage to the fuel-injection system. In the current state-of-the-art, entrained air may be separated from the fuel in fuel-pump and pressure-regulator componentry, and most commonly in the fuel-filter housing. The separated air may be admitted to a fuel-return line of the fuel-injection system, which takes it back to the fuel tank where it is vented to the atmosphere.
The solution summarized above admits of several disadvantages. First, air present in the fuel-filter housing may limit the effective filtration area of the fuel filter, causing inadequate pressurization downstream of the fuel filter at relatively high flow rates. Second, in a modern motor-vehicle system, various components (e.g., heating components) may divert fuel from the fuel-return line back to the engine-supply line. If the fuel-return line carries air that was separated from the fuel, this air will be re-introduced back into the engine-supply line. Third, the componentry used to separate entrained air from the fuel typically does little to dampen the pressure pulsations from the reciprocating fuel pumps of the fuel system. Therefore, additional componentry may be required to deliver a steady flow of fuel to the engine.
Accordingly, one embodiment of this disclosure provides a fuel-air separator having a chamber with an interior side-wall surface and adjacent interior top and bottom surfaces. An inlet of the fuel-air separator opens to the interior side-wall surface to admit fuel and air and to cause the fuel and air to flow helically down and along the interior side-wall surface. A diptube opens to the bottom surface and extends along an axis of the interior side-wall surface to a fuel outlet. An air outlet is included at the top surface of the chamber to release the separated air to the atmosphere. With the disclosed separator installed in a motor-vehicle fuel system, entrained air is effectively separated from the fuel, and in a manner that does not limit the effective filtration area of the fuel filter or re-introduce air into the engine-supply line. In addition, the disclosed fuel-air separator provides effective dampening of pressure pulses caused by reciprocating fuel pumps, enabling a steadier delivery of fuel to the engine.